Circuit interrupter



Nov. 17, 1931. 'r. T. GREENWOOD 1,832,201

CIRCUIT INTERRUP-TER Filed June 29, 1929 filverftor'.

Patented Nov. 17, 1931 UNITED STATES PATENT? OFFICE TALMA T. GREENWOOD,OF EAST TEMPLETON, MASSACHUSETTS, .ASSIGNOR TO CONDIT ELECTRICALMANUFACTURING CORPORATION, OF SOUTH BOSTON, MASSACHUSETTS,

A CORPORATION OF MASSACHUSETTS CIRCUIT INTERBUPT'ER Application filedJune 29, 1929. Serial No. 374,838.

This invention relates to alternating current electric switches andcircuit interrupters andparticularly to a method and means forinterrupting the alternating current circuitinterrupting are that isdrawn between the separable contact members of the switch. Thealternating current are goes out periodically at the end of each halfcycle, when the current passes through zero, and usually isre-established at the beginning of the succeeding half cycle when thepotential across the arc terminals becomes sufliciently great toovercome the resistance of the arc zone.

One of the objects of the present invention is a method and a paratusfor removing the conductin ions rom the arc zone during the time t atthe arc is out while the current is passing through the zero point ofthe wave and for delaying for a determined time the re-establishment ofvoltage across the arc terminals or for increasing the period of timethat the potential acrossthe arc terminals is substantially zero, or isinsuflicient to pass an arc currentthrough the arc zone, so that theion-removin means can have an increased eriod 0 time during which toact, thus to e more effective in building up the dielectric strength ofthe arc zone and thereby 1preventing the re-establishment of the are.

11 carrying out this object of the invention, it is a specific object toimpress a potential on the circuit to be interrupted, which impressedpotential preferably is less than the maximum potential of the circuitand has a greater frequency as, for instance, triple the frequency, sothat it modifies the potential of the circuit to be interrupted andreduces said potential a determined time on 0th sides of the normal zeropoint of the potential wave. The method thus increases the time at whichthe arc terminals are substantially free from potential and thus givesthe ion-removing device an increased period of time during which to actwith greatest effectiveness.

A further object is generally to improve upon circuit interruptingapparatus and methods.

Fi 1 is a diagram illustrating the separab e contact members of anelectric switch practically to zero for terrupt the circuit. Uponseparation of the contact members, an arc is drawn between them, whichare of necessity goes out and, in the ordinary switch, is re-establishedat successive half cycles of the current. Means are provided herein toremove the conducting ions from the arc zone between the separatedcontact members whereby to increase the dielectric strength of themedium in the are zone to such a point that the dielectric strength isgreater than the potential that is impressed on the arcing members,whereby the arc cannot be re-established.

Said means is most effective at the time that the arc is momentarilyextinguished when the arc current passes throughthe zero point of thewave. Said means, as here shown, includes an electrostatic fieldproducing means as a ring 16 which ring surrounds the-arc and the fieldof the ring is effective throughout the arc zone and the space occupiedby the arcing surfaces of the contact members. Said rin is energized bya suitable source, herein iagrammatically illustrated as the battery 18,which source means to act upon the arc zone before t e re-establishmentof the arc is relatively small. In accordance with this invention, meansare provided to dela the buildin up of potential at the normal zeropoint 0 t e potential wave whereby to increase the time that theion-removing means is free'to act unimpeded on the arc zone. Said meansincludes an alternating current generator 20 which energizes the primarywinding 22 of a transformer, the secondary winding of which is connectedand, as here shown, is in series with the power circuit 14. Thegenerator 20 thus impresses upon the power circuit an alternatingpotential which is a function of the potentlal and frequency of thegenerator. Preferably, the frequency of the generator 20 is higher thanthe frequency of the potential in the power circuit 14, preferably bysome multiple such that both potentials pass through their zero pointsat the same time. The generator 20 may, for instance, set up a potentialin the power circuit 14 that is tri le the frequency of the normalpotential 0 said power circuit. The impressed otential acts upon thecircuit potential to atten the wave at the zero point as is indicated inFig. 2. In this figure, 26 represents the potential wave of the powercircuit 14 while 28 represents the high frequency impressed potential.The resultant of the two potential waves gives the potential wave 30which is the one impressed across the arc terminals.

It will be noted that this resultant wave is substantially zero for anumber of degrees on both sides of the zero point of the normalpotential wave 26 as indicated at 32. If both the potential waves 26 and28 are sine waves, the resultant potential wave 30 may not be reducedcomp etely to zero in the region of the normal zero point but at leastthe resultant potential will be so low that it is insuflic'ient tore-establish and support a persistent arc.

The resultant potential in the region of the zero point may be reducedmore completely to zero if the potential waves 26. and 28 are madecomplements of each other at this point as by. having the potential wave28, in an obvious manner, follow a suitable curve that is somethingother than a sine curve. Thus, by accelerating the decay of the tentialwave on one side and delayin the uilding u of potential on the otherside of the norma potential zero, a greatly increased time period isprovided during which the are potential is zero and the ionremovingmeans 16 is free to act unimpedi-' ently upon the arc zone, thus toenhance its efiectiveness.

The method and apparatus herein disclosed for removing ions from thezone of the arc is described and claimed in my copending applicationSerial No. 152,048, filed December 1,1926.

Iolaim:

1. An alternating current circuit interrupter having separable cortactmembers between which acircuit interrupting arc is established uponseparation of said contact members, means to remove ions from the arczone between said separated contact members, and means to delay there-establishment of the arc potential between said separated contactmembers during the reversal of arc polarity including means to modifythe character of the wave of the are potential and to maintain itsubstantially at zero for a definite period of time on both sides of thenormal zero point of its wave.

2. An alternating current circuit interrupter having separable contactmembers between which a circuit interrupting arc is established uponseparation of said contact members, means to remove ions from the arczone between said separated contact members, and means to maintain thearc potential substantially at zero for a definite period of time onboth sides of the normal zero point of its wave.

3. An alternating current circuit interrupter having separable contactmember's between which a circuit interrupting arc is established uponseparation of said contact members, means to remove ions from the arczone. between said separated contact members, and means to supply thearc with current at an alternating potential which has substantiallyzero value for definite periods of time.

4. An alternating current circuit interrupter having separable contactmembers between which a circuit interrupting arc is established uponseparation of said contact members, means acting when the arc current iszero to remove ions from the arc zone between said separated contactmembers, and means to delay the re-establishment of the are potentialbetween said separated contact members during the reversal of arcpolarity including means to impress an alternating potential upon theare potential, said alternating potential having a value and being at afrequency which differs from that of the frequency of the are potentialby such values as to maintain the are potential substantially atzero fordefinite periods of g time.

5. An alternating current circuit interrupting apparatus havingseparated arc terminals between which an alternating current are issupported,.means acting when the arc current is zero to removeconducting ions from the arc zone between said terminals, and means tosupply said terminals with an alternatin potential which is maintainedsubstantially at zero for definite periods of time.

6. An alternating current circuit interrupting apparatus havingseparated arc terminals between which an alternating current arc is suported, means to remove conducting ions rom the arc zone between saidterminals, and means to supply said terminals withan alternatinpotential which is at a value that is insu cient to pass an arc currentbetween said terminals for predetermined periods of time.

7. The method of interrupting an alternating current electric arc whichconsists in supplying the arc with an alternating potential which issubstantially at zero for predetermined periods of time, and removingions from the arc zone during such periods.

8. The method of extinguishing an alternating current are which consistsin supplying the arc with a potential that for definite periods of timehas a value lower than that necessary to initiate the arc, and removingions from the arc zone during such periods.

9. The method of interrupting an alternating current electric are whichconsists in supplying the arc with an alternating potential, modifyingsaid potential by an impressed alternating potential of differentfrequency such as to provide a resultant are potential that issubstantially at zero for predetermined periods of time, and removingions from the arc zone during such periods.

In testimony whereof, I have signed my name to this specification.

TALMA T. GREENWOOD.

